Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, e.g., of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfer and fixing. Ink jet printing mechanisms can be categorized by technology as either drop on demand ink jet (DOD) or continuous ink jet (CIJ).
The first technology, “drop-on-demand” (DOD) ink jet printing, provides ink drops that impact upon a recording surface using a pressurization actuator, for example, a thermal, piezoelectric, or electrostatic actuator. One commonly practiced drop-on-demand technology uses thermal actuation to eject ink drops from a nozzle. A heater, located at or near the nozzle, heats the ink sufficiently to boil, forming a vapor bubble that creates enough internal pressure to eject an ink drop. This form of inkjet is commonly termed “thermal ink jet (TIJ).”
The second technology commonly referred to as “continuous” ink jet (CIJ) printing, uses a pressurized ink source to produce a continuous liquid jet stream of ink by forcing ink, under pressure, through a nozzle. The stream of ink is perturbed using a drop forming mechanism such that the liquid jet breaks up into drops of ink in a predictable manner. One continuous printing technology uses thermal stimulation of the liquid jet with a heater to form drops that eventually become print drops and non-print drops. Printing occurs by selectively deflecting one of the print drops and the non-print drops and catching the non-print drops. Various approaches for selectively deflecting drops have been developed including electrostatic deflection, air deflection, and thermal deflection.
Recently developed ink jet printing systems utilize drop forming devices associated with individual nozzles or groups of nozzles to control the formation of drops. For example, recently developed continuous ink jet printing systems utilize drop forming devices associated with individual nozzles or groups of nozzles to control breakup of the liquid streams flowing through nozzles into drops in response to the print data. U.S. Pat. No. 6,474,794, issued to Anagnostopoulos et al. on Nov. 5, 2002, and entitled INCORPORATION OF SILICON BRIDGES IN THE INK CHANNELS OF CMOS/MEMS INTEGRATED INK JET PRINT HEAD AND METHOD OF FORMING, describes a method for fabricating nozzle plates that can be used in these recently developed continuous inkjet systems. It involves forming integrated circuits for controlling the operation of the printhead on a silicon substrate, forming a thin membrane of insulating layers with nozzles and drop forming devices formed in the membrane, and forming a series of ink channels through the silicon substrate, the each of the ink channels being aligned with a nozzle. The silicon substrate includes ribs that separate the individual ink channels and provide strength to the nozzle plate.
While this nozzle plate construction is effective and extremely well suited for its intended application, there are difficulties associated with etching the individual ink channels through the silicon. High aspect ratio ink channels can be etched through the silicon substrate using a Deep Reactive Ion Etching (DRIE) process. However, the etch efficiency and straightness/quality of the sidewalls decreases with increasing feature aspect ratio, which can limit the device design and performance. As such, there is an ongoing need to improve nozzle plate performance and nozzle plate construction.